Boating enthusiasts, mobile home owners and other users of trailers know the difficulty of aligning and attaching a trailer to the towing vehicle. In particular, vertically-aligning the inverted socket of a trailer hitch to the mating ball on the drawbar of the towing vehicle is hampered by poor visibility of the trailer hitch and the tow bar when using mirrors and/or physically turning around. A second person can be used as an observer to relay instructions to the driver, but there are times when a second person is not available. Since the towing vehicle typically cannot be manually moved sideways, it is the trailer which must be moved manually into final position for hitching when the two are nearly, but not truly aligned. For small, light-weight trailers, this might not be much of a problem unless, of course the person doing the manual moving has physical difficulty in doing so. The trailer may be physically pulled to where the towing vehicle is parked or the towing vehicle may be backed-up to position the ball as close to alignment with the socket as possible and then the trailer manually moved to bring the socket into final alignment above the ball. These light-weight trailers typically have either an infinitely-adjustable vertical jack or a vertical support pole with fixed pin-adjustable heights to maintain the hitch at a particular height when the trailer is not attached to a towing vehicle. In the case of trailers with the support post, after the ball and socket are positioned, someone must lift the trailer tongue and simultaneously remove a pin which supports the tongue. The socket is then lowered onto the ball, the latch which locks the ball and socket together is locked, the support post is lifted to clear the ground during travel and pinned in place and the safety chains are attached. In the case of trailers which have a jack, the procedure is similar except that rather than lifting the tongue, removing the pin and pinning the support post in the raised position, no lifting is required and the jack is used to lower the socket onto the ball. The jack is then pivoted away from the ground and locked in that position. For larger, heavier trailers, particularly those trailers with multiple sets of axles and tires such as used with mobile homes and large boats, the above procedure is difficult or impossible for one person to do. Typically, someone outside of the vehicle must help direct the vehicle driver so as to position the ball close enough to the mating socket and minimize the amount of manual movement necessary during final-alignment of the ball and socket. If there is nobody to help direct the driver, oftentimes multiple cycles of backing up, exiting the vehicle to check positioning, reentering the vehicle, and repositioning the vehicle are necessary. That consumes time. While most large trailers have a jack with a swivelable ground-contacting wheel to eliminate lifting of the trailer tongue, two people may still be required to pull the socket into position above the ball. The present invention is designed to minimize or eliminate the need for an observer to help direct the tow vehicle driver and to move the trailer socket sideways into vertical-alignment with the ball automatically using the tow vehicle's power.